Magnesium production



Patented Dee. 19, 1944 VNITED STATES PATEN'I'J OFFICE.

2,365,386 MAGNESIUM PRODUCTION Robert A. Boyer,- Dearborn, and Elbert E. Ensign,

.. Ypsilanti, Mich, assignors to Ford Motor Company, Dearborn, Mich, a corporation of Dela ware No Drawing. Application September 12, 1942,

Serial No. 458,128

Roam/(01.1547) This invention relates to the production of nesium'ores, and more particularly the production of magnesium by the ferrosilicon process aided by catalytic action.

Heretofore, metallic magnesium has been chiefly produced commercially by the electrolytic process involving a fused magnesium chloride bath; Although other processes such as the ferrosilicon reduction, carbon reduction and reduc unfeasible for largerscale production. In many casesthe use of these processes has been remagnesiumby the thermal reduction of mag* I tion by other metals have been greatly publicized, and although-these processes have produced magnesium metal in laboratory experiv ments, they have been found to be economically strained from commercial success by reason of.

unforeseen adverse conditions and difficulties that are inherent with large-scale production and lack oi suitable equipment with the ability to withstand the stresses and strains imposed on it by the process. The ferrosilicon process has been one of'those processes which has been so hampered. Satisfactory yield in this process is governed by temperature of the reaction since other conditions such as time and pressure can be more easily overcome. Thus, the temperature range at which the greatesuefiiciency is obtained is beyond the temperaturerange of the alloys which are used in constructing the equipment for the process. V

The effect of the temperature gradient is clearly -shown in the following chart in which the pressures and time elements are maintained relatively constant: a

Temperature yield chart 4 Percent yield From the above results, it is seen that theoretical yields are only approached at the higher I temperatures.

However, the heat and oxidadon-resistant alloys such as nichrome are not suitable tor the upper of the above temperature'range since at the highertemperatures the eflective life of the retort may be only several hours. Moreover, even though at lower temperatures the life is greatly increased the process also becomes I economically unfeasible due to the extremelylow yield obtainable.

processing, as pointed out'by this invention, are

It is therefore an object of this invention to produce improved efllciency in a ferrosilicon reduction of magnesium ores, said improvement to be effective throughout the temperature range inherent of the process. Essentially, yields may be derived at a given temperature by this'in'vention which, formerly, could only be obtained at a much higher temperature. 4

The data, comprising temperature-yield chart above was obtained from numerous tests which we choose to term as the standard run. The

standard rim .consists of a briquetted charge celerate the reaction of the ferrosilicon process such as to increase or decrease the yield. This.

is brought about by incorporating into. the furnace charge certain catalytic agents-producing the desired effects. Catalytic agents which we have found to work successfully are: I

Negative catalytic agents Positive catalytic agents Oxides of iron Aluminum oxide I Sodium chloride Beryllium oxide aleium carbonate Ceric oxide Magnesium carbonate Titanium dmxide Silica Zirconium oxide Boric acid Kyanitc Kaolin As it is the purpose of this invention to in- I crease the efliciency of the ferrosilicon process. the negative catalytic agents, may be disregarded. Howevenfrom this data one is able ,to predict the'efliciencyof the process whcn the charge contains such compounds mi ute quantities.

' provements in the'production or magnesium best practiced in the conventional ferrosilicon process which consists chiefly of a tubular retort furnace whose ends may be sealed and may be maintained underreduced pressures. tubular retort must be constructed of analloy having supreme heat-resisting and antioxidaeven in very a .librium condition much faster.

tion properties since it has been shown that the greatest yield may be obtained at the higher temperatures. The heating may be accomplished by conventional means such as external gas heat-- ing, glow bars, molten, fused baths and by other conventional means.

The charge of raw materials of this invention consists of the following:

C1 Parts Calcined dolomite 75 to 85 Ferrosilicon to Catalyst to 5 The dolomite, ferrosilicon and catalyst in finely ground form are thoroughly mixed in the above ratios and then briquetted. The briquettes are then charged into a tubular-retort and are subjected to temperatures of from 2,100 to 2,400 F. under a pressure of about 75 to 200 microns. A preferred form of the above formula comprises:

Parts Calcined dolomite 81 Ferrosilicon 19 Catalyst 1 foreign substances is not clearly understood.

This reaction is of such a nature that no one, to

our knowledge, has as yet seen fit to present an explanation. This type of complicated reaction in which a solid produces a catalytic reaction on another solid may probably be best interpreted in the light of interfaces as explained in Treatise on Physical Chemistry, by Taylor. Taylor explains that the solid-to-solid interfacial activity or the catalytic action of one solid on another whereby a product of a different phase may be formed is not uncommon. As a further explanation of this in relation to our process it is thought these interfaces bring about a true equi- Thus in our case catalytic action occurs between a solid dolomite or other magnesium-bearing ores and a solid oxide or like catalyst to produce magnesium vapor while the residue remains in a solid state throughout the reaction.

Another explanation may be that there occurs among the ingredients a fusion and the fused product tends to hasten the liberation of ma nesium by interfaces. This may be further explained by observing the reaction of some negative catalytic agent such as oxides of iron and silica and eliminating these negative catalysts by means of positive catalytic agents. It is generally believed that the two antagonistic catalysts impossibility prior to processing. Therefore, it follows that the yield is increased by elimination of these retardants, or by the use of counteracting elements.

It should also be noted that the interfaces and other reactions of the process occur in the solid phase. The ability of the residue to remain in a solid state is of prime importance, particularly in the process using a horizontal tubular retort. It would be extremely difiicult to maintain a retort free from' an insulating layer of residue if the charge were to become molten, or to charge and discharge the retort if the residue were likely to become tacky or gummy.

However, it has been suggested in U. S. Patent No. 2,224,160 that adding certain ingredients, which will reduce the melting temperature of the residue, is a decided advantage. This invention relates primarily to ,the maintenanceof the slag through certain percentages having a low melting point, so that the residue may be removed in the molten state. 7

Our invention may be briefly summarized and differs from the above patent in that we incorporate in our charge a very small percentage of a catalytic agent whereby solid-to-solid interfaces between the magnesium-bearing ore and the reducing agent ferrosilicon occurs, thus increasing the yield and eiiiciency. We have attempted briefly to explain the physical or chemical phenomena in the solid-to-solid reaction when metallic oxides are used as catalysts or accelerators.

Other advantages will readily occur to those familiar with this art and it is the applicants intention, although some changes may be made in the process described without departing from the spirit of our invention, to cover by our claims such claims as may easily be included within the scope of this invention.

We claim as our invention:

1. In the process for the production of metallic magnesium, a charge comprising magnesium bearing ore, ferrosilicon and a catalyst, said catalyst being one of aluminum oxide, beryllium oxide, ceric oxide, titanium dioxide and zirconium oxide, said charge subjected to a temperature of greater than 2,100 F. at a pressure of less than 1,000 microns.

2. In the process for the production of metallic magnesium a charge comprising:

Parts Calcined domolite 75-85 Ferrosilicon 15-25 Catalyst 4- 4 said catalyst being one of aluminum oxide, berylhum oxide, ceric oxide, titanium dioxide and zirconium oxide, said charge subjected to a temperature of greater than 2,100 F. at a pressure of less than 1,000 microns.

3. In the process for the production of metallic magnesium a charge comprising:

V Parts Calcined domolite 81 Ferrosilicon 19 Catalyst l said catalyst being one of aluminum oxide, beryllium oxide, ceric oxide, titanium dioxide and zirconium oxide, said charge subjected to a temperature of greater than 2,100 F. at a less than 1,000 microns.

4. In the process for the production of metallic magnesium "a charge comprising calcined dolonnte, ferrosilicon and A1203, said charge subpressure -of Jected to a temperature of greater than 2,100 F. at a pressure of less than 1,000 microns.

5. In the process for the production of metallic magnesium a charge comprising calcined dolomite, ferrosilicon and T102, said charge subjected to a temperature of greater than 2,l00 F. at a pressure of less than 1,000 microns.

6. In the process for the production of metallic magnesium a charge comprising calcined dolomite, ferrosilicon and Al2O3.SiO2, said charge subjected to a temperature of greater than 2,100 F. at a pressure of less than 1,000microns.

'7. The process for the production of metallic magnesium comprising a charge of magnesiumbearing ore, ferrosilicon and a catalyst, said catalyst being one of aluminum oxide, beryllium oxide, ceric oxide, titanium dioxide, and zirconium oxide, heating said charge in a sealed retort above 2,100 F. at a pressure of less than 1,000 microns to liberate magnesium vapors, withdrawing said vapors from said retort, and condensing said vapors t0 reguline magnesium.

8. The process for the production of metallic magnesium comprising a charge of Parts Calcined dolomite 75-85 Ferrosilicon 15-25 Catalyst A- 4 is Al20a.SiO2.

said catalyst being one of aluminum oxide, beryllium oxide, ceric oxide, titanium dioxide and zirconium oxide, heating said charge in a sealed retort above 2,100 F. at a pressure of less than 1,000 microns to liberate magnesium vapors,

withdrawing said vapors from said retort, and

condensing said vapors to reguline magnesium.

9. The process for the production of metallic magnesium comprising a charge of Parts Calcined dolomite 81 Ferrosilicon 19 Catalyst 1 ROBERT A. BOYER. ELBERT E. ENSIGN. 

